Spin duplicate gives parts - how to spin a complex part of a pipe?
Method 1:

Build the unstretch parts first, then bridge the loops among them:

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Demo file for Method 1 is here.

PROS: Can well satisfy what you need in this particular case.

CONS: Quite a bit basic knowledge on blender is needed.



Method 2

Model stretching and unstretching units separately, then bend them individually with the same curve:



Demo file for Method 2 is here.

PROS: Relatively easy to accomplish.

CONS: Unavoidable intersections in final mesh.